Although dental amalgams remain the most popular restorative material today, many questions have arisen relating to mechanical, corrosion and biocompatibility of contemporary materials. Our objective is the development of new compositional concepts in dental amalgam through the addition of Pd and other noble metal alloys in small concentrations. Modification of compositions and resulting microstructures of amalgams should result in dental restoratives of markedly improved mechanical and corrosion properties. Given the apparent affinity between Pd and Hg, it is hoped that the Hg vapor pressure over these amalgams will be significantly reduced. Both single composition and blended amalgams will be fabricated from alloys utilizing Pd substitution for major amalgam alloy components (Ag,Cu,Sn). Structural and phase relationships of resulting amalgams will be determined by modern ultrastructural techniques. New reaction products, once identified, will be fabricated and likewise studied. Amalgams whose improved properties have been already determined will be further refined through optimization of clinical variables. Mechanisms of property improvement associated with the formation of new Pd reaction products will be determined by aid of ultrastructural analysis. Conventional electrochemical techniques will be supplemented by atomic absorption to determine changes in released ions through compositional modification. Hg vapor pressure over amalgams and constituent phases will be measured. Controls will be blended and single composition contemporary commercial amalgams. Amalgams whose Pd concentrations have been optimized will be further refined by minor additions of other noble metals and similarly studied.